Annular magnets for rotor position estimation

Abstract

A magnetic position sensing system includes at least one annular magnet mounted to a surface of a rotating body. The annular magnet includes a first end, a second end, an inner diameter surface, and an outer diameter surface. The inner diameter surface and outer diameter surface define a radial thickness therebetween, and the radial thickness varies from the first end to the second end.

The invention claimed is: 
     
       1. A magnetic position sensing system comprising:
 a first annular magnet mounted to a first surface of a rotating body; 
 a second annular magnet mounted to a second surface of the rotating body, the second surface being generally perpendicular to the first surface; 
 wherein each of the first and second annular magnets comprises:
 a first end; 
 a second end; 
 an inner diameter surface; and 
 an outer diameter surface; 
 wherein the inner diameter surface and outer diameter surface define a radial thickness therebetween, the radial thickness varying from the first end to the second end. 
 
 
     
     
       2. The system of  claim 1 , wherein the at least one of the first and second annular magnets further comprises a forward surface and an aft surface, and an axial thickness between the forward surface and the aft surface. 
     
     
       3. The system of  claim 2 , wherein the axial thickness of the at least one of the first and second annular magnets decreases from the outer diameter surface to the inner diameter surface in a region adjacent the first end. 
     
     
       4. The system of  claim 2 , wherein the axial thickness of the at least one of the first and second annular magnets increases from the outer diameter surface to the inner diameter surface in a region adjacent the second end. 
     
     
       5. The system of  claim 2 , wherein the axial thickness of the at least one of the first and second annular magnets increases from the outer diameter surface to the inner diameter surface in a region adjacent the first end. 
     
     
       6. The system of  claim 2 , wherein the axial thickness of the at least one of the first and second annular magnets decreases from the outer diameter surface to the inner diameter surface in a region adjacent the second end. 
     
     
       7. The system of  claim 1 , wherein the at least one of the first and second annular magnets comprises a plurality of segments, each of the segments having a first end and a second end, and a varying radial thickness between the first end and the second end. 
     
     
       8. The system of  claim 1  and further comprising at least one Hall effect position sensor proximate the at least one of the first and second annular magnets. 
     
     
       9. The system of  claim 1 , wherein the at least one of the first and second annular magnets is formed from a material selected from the group consisting of rare earth elements, non-rare earth elements, and combinations thereof. 
     
     
       10. The system of  claim 1 , wherein the first surface is an outer diameter surface of the rotating body. 
     
     
       11. The system of  claim 10 , wherein the second surface is an end face surface of the rotating body. 
     
     
       12. The system of  claim 11 , wherein the first end of the first annular magnet is offset from the first end of the second annular magnet. 
     
     
       13. A method of making a magnetic position sensing system, the method comprising:
 positioning a first annular magnet on a first surface of a rotating body; 
 positioning a second annular magnet on a second surface of the rotating body, the second surface being generally perpendicular to the first surface; 
 wherein each of the first and second annular magnets comprises:
 a first end; 
 a second end; 
 an inner diameter surface; and 
 an outer diameter surface; 
 wherein the inner diameter surface and outer diameter surface define a radial thickness therebetween, the radial thickness varying from the first end to the second end. 
 
 
     
     
       14. The method of  claim 13  and further comprising: positioning at least one position sensor proximate the at least one of the first and second annular magnets. 
     
     
       15. The method of  claim 13 , wherein the first surface is an outer diameter surface of the rotating body. 
     
     
       16. The method of  claim 13 , wherein the second surface is an end face surface of the rotating body. 
     
     
       17. A method of estimating a position of a rotating body, the method comprising:
 positioning a first annular magnet on a first surface of a rotating body; 
 positioning a second annular magnet on a second surface of the rotating body, the second surface being generally perpendicular to the first surface;
 wherein each of the first and second annular magnets comprises:
 a first end; 
 a second end; 
 an inner diameter surface; and 
 an outer diameter surface; 
 wherein the inner diameter surface and outer diameter surface define a radial thickness therebetween, the radial thickness varying from the first end to the second end; 
 
 
 sensing, using at least one position sensor placed proximate the at least one of the first and second annular magnets, a magnetic flux density of the at least one of the first and second annular magnets, the magnetic flux density corresponding to the radial thickness of the at least one of the first and second annular magnets; and 
 calculating the position of the rotating body based on the sensed magnetic flux density.